1. Field of the Invention
The present invention relates to an improved process for neutralizing the acid present in an air conditioning or refrigeration (hereinafter, AC or R) system. More particularly, the invention relates to a process for introducing a neutralizing agent into such systems to reduce the presence of acid and thereby reduce the likelihood of compressor burnout.
2. Related Art
Air conditioning and refrigeration (AC or R) systems of all shapes and sizes are in common use throughout industry, commercial establishments, public buildings and residences. Such refrigerant compressor systems can be generally characterized as systems which circulate a compressor fluid comprising a lubricating oil and a refrigerant type of gas that is compressible into a liquid and which is then expanded for absorption of heat. The most common refrigerants used at this time are chlorofluorocarbons (CFCs), more specifically R-11, which is trichlorofluoromethane, R-12 which is dichlorodifluoromethane, and R-22 which is chlorodifluoromethane. The lubricating oil is usually a highly refined naphthenic mineral oil, commonly referred to as refrigeration oil.
A diagrammatic view of a typical AC or R system is shown in FIG. 1. In this typical system, a hermetically or semi-hermetically sealed motor compressor 1 houses an electric motor driven pump that compresses an enclosed suitable refrigerant gas which is liquified and circulated throughout the closed system. The refrigerant passes through a series of devices via a pipe system, typically copper tubing, and carries with it a small portion of the compressor lubricating oil. The refrigerant is first propelled as a compressed, pressurized, hot gas into the high pressure (liquid) side 2 of the system. There, it passes through a muffler 3, a Schrader valve 4, and into a condenser coil unit 5 where it is radiatively cooled in a sufficient amount to condense into a liquid. It then passes through a head pressure control 6 and collects in a liquid refrigerant receiver 7 before moving through a series of devices, including a high pressure side valve 8, a liquid line filter-drier 9, a sight glass 10, a liquid line solenoid valve 11 and a liquid line stabilizer 12. The pressurized liquid refrigerant is then passed through an expansion valve 13 where it is atomized to remove its remaining latent heat and to refrigerate the gas by heat of vaporization. At this point, the cold gas is drawn into the low pressure (suction) side 21 of the system and through an evaporator coil unit 14 where it further expands and radiatively reheats by absorption, cooling the surrounding air being drawn over the coil by heat exchange. Pressure between the high and low pressure sides of the system is controlled by a constant high-low pressure regulator 15. The reheated gas is then discharged through a series of devices, including an evaporator pressure regulator 16, an accumulator 7, a suction line filter-drier 18, a low pressure side control 9 and a low pressure side valve 20 before completing the closed circuit by entering the intake of the motor compressor 1. Depending upon design and sophistication of the AC or R system, other accessory devices may also be found in the system, such as additional pressure regulators and controls, multiple stage cooling coils, manifolds, assorted types of valves and sight glasses, heaters, oil separators, sensors or vibration dampeners.
A major problem with AC or R systems is recurring compressor burnout. The term compressor burnout is used to describe a disabling electrical failure in the compressor's electric motor or related electrical components within the system. Burnout can occur from a variety of causes, including direct damage to the electrical coils of the motor or other electrical system components, or from strain on the motor arising from operating at too high a temperature, at the wrong pressure and/or with an incorrect electrical power supply. While several factors may be the cause of compressor burnout, one of the most common causes is the formation of acid in the compressor fluid.
Acids are generally formed in the compressor fluid by the presence of contaminants and moisture, or the breakdown of refrigerant, refrigeration oil and/or degradation of system parts, neither of which processes can be completely avoided. The contaminants and moisture, along with system operating conditions tend to partially break down the chlorofluorocarbons comprising the compressor fluid, releasing free halogen ions. These ions then combine with moisture to form acids which subsequently attack internal system parts. A major factor in this acid attack is that the internal structure of the AC or R system generally comprises various different materials that are susceptible to acidic attack, including steel, copper and copper alloys, aluminum, various synthetic seals, terminals and insulators. Once acids have formed in the AC or R system, they can cause corrosion and deterioration of various system parts, forcing the compressor motor to work harder, causing direct damage to the compressor motor itself, or causing leaks to form which allow moisture to enter the system promoting further acid formation. Regardless of its source, the presence of acid can eventually result in compressor burnout.
The potentially damaging effects of acid in the AC or R system are well recognized by the industry. Several acid test kits are commercially available which enable one to monitor the acidity of the compressor fluids. The higher the acidity of the fluids, the more likely a compressor burnout will occur.
Once compressor burnout has occurred, the compressor must either be repaired or, more commonly, completely replaced. However, repairing or replacing the compressor does not solve the problem since residual acid contamination is usually still present in other components of the AC or R system, having been circulated and deposited throughout the system by the pumping action of the previous compressor. This residual acid, in conjunction with the system's normal operating conditions, leads to additional acid formation. Therefore, if acid is still present, chemical attack will resume anew and it is simply a matter of time until the new compressor experiences a subsequent burnout. It is not uncommon for this burnout cycle to continue over time, requiring multiple compressor repairs or replacements.
Repairing or replacing compressors has become increasingly more expensive, due in part to recent federal regulations regarding the release of CFC and other halogenated-type refrigerants into the atmosphere. To avoid releasing these refrigerants, various recovery, reclaiming or recycling machines are used which can remove the refrigerant along with entrained refrigeration oil from the system without exposing the fluid or gas to the atmosphere. But, such methods can be extremely expensive. The cost of refrigerants has also increased due to the environmental regulations, and some manufacturers have stopped making certain CFC-type refrigerants altogether. Thus, various methods have been devised to purge the AC or R system of acid whenever the compressor must be repaired or replaced in order to help diminish the likelihood of compressor burnout.
One of the most common methods for purging the system of acid has been to flush the system with some type of refrigerant whenever a compressor must be repaired or replaced. The most common refrigerant used for this purpose has been R-11; however, the same environmental concerns discussed above for using R-11 as a refrigerant apply to the use of R-11 as a flushing agent. R-11 is also becoming extremely expensive and difficult, if not impossible, to obtain in many sections of the nation. Alternative flushing agents include nitrogen, carbon dioxide and pressurized air. However, these gases have little capacity to solubilize the acidized compressor fluids and are, therefore, relatively ineffective at acid removal. Further, unless used in an absolutely dry state, these compressed gases will introduce moisture into the system which will help promote acid formation.
Another problem associated with trying to flush an air conditioning or refrigeration system is that some acid may remain in the system despite the flushing efforts. Once acid has begun to form, it can spread throughout the compressor fluid and into any of the system's internal components. When the fluid is flushed, some acid is likely to remain in the system, either in the reservoirs of lubricating oil, as surface deposits, or attached as corrosion to the seals or other internal parts, or simply in some small pocket of compressor fluid which did not flush. Any acid which remains in the system will likely resume chemical attack of system parts and precipitate the formation of more acid once new compressor fluid is added and the system is running again.
Since flushing the system is recognized in the industry as inadequate to solve the acidity problem, other methods have been devised to combat the problem of acid formation. Many repairmen attempt to "triple-flush" a system, which may be more effective than a single flush, but has the same inherent deficiencies stated above. Another common method for purging acid is to replace the refrigeration oil either once or repeatedly in order to dilute the residual acid in the system. Some times this method is combined with the R-11 refrigerant flushing method. In addition to the inherent deficiencies noted for the R-11 method, replacement of refrigeration oil is similarly ineffective at completely removing acids. Additionally, such procedures are expensive and produce waste oil which must be disposed of as regulated hazardous waste.
Yet another common method of reducing the deleterious effects of acid is the use of filter-driers (See, e.g. in FIG. 1 9, 18) in an AC or R system. Installation of common filter-driers is a widely recognized standard practice when repairing AC or R systems, regardless of the mode of failure. Common filter-driers driers are designed to remove contaminants and water from the compressor fluid as it circulates through the system. However, these devices are not effective at removing acid unless special composition filter-drier elements are used. Even then, the acids are merely absorbed into, or adsorbed onto, the filter element and are not entirely removed from the system. If the acids are dislodged from or manage to bleed through the filter element, or if the element becomes saturated, then the problem still remains. Additionally, the filter-drier must be checked and maintained with periodic filter element replacement to remain effective, as a partially blocked filter will add additional strain to the system causing the compressor motor to work harder and likely create more acid.
Since the presence of acid in the compressor fluid is a major cause of compressor burnout, effective neutralization of the acid in the system would be expected to contribute to a reduction of burnout problems. One such method is disclosed by Fabian in U.S. Pat. No. 3,119,244. Fabian discloses a refrigerant treatment element which is a cylinder containing an amount of soda, namely sodium bicarbonate. The treatment element is designed so that the compressor fluid comes into contact with the soda and any acid is thus neutralized. A non-solution form of a buffered acid salt is used as a weak neutralizing agent. The agent is restricted to a predetermined quantity in a fixed location on the compressor high pressure side of a refrigeration system. Acid contamination within the system is then required to migrate as part of the compressor fluid completely around the system in order to be neutralized at that fixed location. In order to undergo neutralization, the acid must then intimately contact previously unreacted sodium bicarbonate within the constraints of the dead-end lower chamber of a refrigerant treating element and remain there, coincident with moisture, for sufficient time for the neutralization reaction to occur.
Additionally, predetermined quantities of sodium bicarbonate may be stoichiometrically insufficient to neutralize the amount of acid formed in any given compressor. Because the neutralization agent is only at one very restricted access location, and because the neutralizing compound is not in solution and is not inherently a strong reactant, all acid within a system may not come in contact with the fixed neutralizer in order to undergo reaction. In fact, some acid species may not react with the soda at all regardless of contact. Furthermore, even where that acid which is capable of reacting with the soda neutralizer does actually contact the neutralization agent it may not do so for a sufficient period of time to be effectively neutralized. Further, any neutralization reactions that do occur with the soda can produce insoluble salts which could shield remaining unreacted sodium bicarbonate from contact and further reaction with any remaining acids. Lastly, acid reactions with sodium bicarbonate often produce carbon dioxide. The presence of this gas in an air conditioning or refrigeration system is detrimental in that it can result in system over-pressurization, heat transfer efficiency losses and/or recombination with any moisture present which can re-introduce a mild acid into the system.
U. S. Pat. No. 5,015,441, issued to Uratani on May 14, 1991, discloses a method for preventing corrosion of internal metal surfaces of air compression devices comprised of electrolytically generating a basic aqueous solution, then injecting that solution under pressure into the operating air compressor system to neutralize acidic water condensate which may be formed within the system. This method, however, would not work well with air conditioning or refrigeration systems because any introduction of water, however slight, into such a system can cause the CFCs to partially breakdown releasing halogen ions and leading to the production of more acid. AC or R systems are not designed to compress externally drawn air for subsequent discharge. Rather, they are designed to operate as closed loop, sealed fixed volume liquid/vapor heat transfer devices. Their internal operating environment is entirely different and the injection of large quantities of water (as for air compressors) would be catastrophic for AC or R systems. Not only would acid content generation and refrigerant degradation be grossly affected, but the system's fixed liquid volume capacity would be exceeded causing heat transfer efficiency problems. Additionally, water would interfere with the function of exposed internal electrical components leading to rapid electrical system failure, and reduction in refrigeration oil lubricity which could lead to early mechanical failure.
Thus, there is a need for a method for neutralizing the acid in an air conditioning or refrigeration system which more effectively eliminates the acid and does not introduce water or other contaminants into the system. In particular, compositions and methods are needed which circulate agents capable of neutralizing the types of acids responsible for compressor burnout to all affected internal surfaces of AC or R systems.